mtntopgeo

My Feedback: (12)

Know that this ain't 1/2a, but since an overabundance of talent hangs out around here, wanted to try here first. ...... Got hold of an old used Super Tiger x11 rc plain brg. engine, & started it up today. Great compression, starts easy, but lower performance than I expected. 15,500 on 20% nitro, 20% castor, with a 7x4 MAS prop. Tried some 33% nitro, & it got up to 16,200, running lean. Couldn't richen it up any more. The carb throat looks very large, and I'm thinking "crankcase pressure". Before getting carried away & going off the deep end, thought I'd ask for advice. ..... Am I expecting too much? (One of my Enya .09-IVs will turn the same prop at 15,800 RPMs) How much nitro do these things like? 20% castor O.K.? Help! Someone point me in the right direction!!! .......... George K.

combatpigg

My Feedback: (3)

I'm not familiar with that exact model engine, but it would help to know what prop it was trying to turn. If you couldn't back the needle out far enough to richen it up, then it either has one or more airleaks, or a flaw in the fuel delivery system, starting at the tank. It was common to see a back plate bolt replaced with a pressure tap if you are running WOT.

mtntopgeo

My Feedback: (12)

Thanks CP, I'll do a bubble test on it. If the Engine passes the test, then I'll try to use crankcase pressure. ........ George K.

combatpigg

My Feedback: (3)

Old, high compression SuperTigres don't need much nitro to run well. 15% is all I've ever run through them. I'm mainly familiar with the high performance .15, they really scream. This is a plain steel P/L engine, so it is a good one for amatuer machinists to practice making parts for.

Dan Vincent

Some years ago F/F guys were yanking the RC carb and using a straight venturi.

They were getting some real screamers and these Supertigre .11 engines were popular for a while.

mtntopgeo

My Feedback: (12)

Thanks for the input. This thing went through the "bubble test" ok. Gonna try crankcase pressure. Will post if results are good. If not, the engine will find a place in the workbench drawer, right next to the K&B .18! .......... George K.

combatpigg

My Feedback: (3)

I would pull the glow plug and work some solvent through it, like WD 40 or gun cleaning solvent. Use your electric starter to crank the solvent through, or chuck the prop nut into an electric drill. Every once in a while douse the crankcase through the intake. Maybe this will help? An .11 doesn't have a great selection of props, a 7x3 is as big as it will probably turn decently. APC has some oddball sizes, maybe they have some props in the 6.5x4 or so range?
The right size prop can make all the difference, get this sucker revvin', then build a little racer for it!

mtntopgeo

My Feedback: (12)

OK, I'm back. After doing a bubble test (again, & again), saw a little foam (used dish soap & water) forming at the crankcase cover. Had to lap the crankcase (about .004" lo spot between upper bolts) & use some sealer to stop that show. No real difference in performance. That BIG carb kept bothering me, so I shimed up th fuel tank so that the fuel level was slightly above the needle. This allowed me to adjust the needle when on the 33% fuel, but little increase of RPMs. Cut the 7x4 MAS down to 6.5 inches diameter (per CP's guess at prop size). Again a slight increase in RPMs, but nothing noteworthy. Changed out the no-name idle-bar glo-plug ( It looked OK, but I didn't know what else to do.) with a FOX Miracle Plug. That really perked things up. (Don't ask me "why".) 17,600 on 15%, & 18,200 on the 33% stuff. Idle was smooth at 6000, & not so good at 5000. While this doesn't equal Enya CX performance, It is certainly acceptable for some sport flying. I'm still lost as far as the the big carb is concerned. I reach max RPMs with the carb just a little more than 50% open. Either the manufacturer wanted this thing to run at 25K, or they didn't want to make a smaller carb for this small engine. QUESTION; .... Do I keep going to a smaller prop & try for more RPM's (I like to stay with planes with at least a 36 to 38" wiingspan.... helps these old eyes) or, do these RPMs sound reasonable for this engine??????? ...............

combatpigg

My Feedback: (3)

I think you're getting there, but you would have better luck with a lighter [wood] prop. Wood is easier to work, also. Cutting down the diameter isn't enough, get out your exacto and start scraping, skiving, shaving, [whatever you want to call it] to thin the blades down. You also want to regain the props original aspect ratio before you chopped it down. Always work the top of the blade, leave the back side alone. There aren't going to be any off the shelf props that are optimal for this oddball engine. At some point this engine will come to life.....I wouldn't go below 6.5" of diameter, or you might as well park it and run a .074. If it won't crank out closer to 20,000 with a little more prop work, then I would be surprised. If it tends to fire up backwards alot, then decrease the nitro.
The photo doesn't really demonstrate how thin the blades are, this prop is a 7x5 for a ST .15.

BTW, with the engine cold, prime it through the exhaust and slowly bring it up to TDC, then count how long the cylinder stays pumped up. If it bleeds off within less than 2 seconds, yer beating a dead horse.

Yuu

Big Carb? Could someone have put a .15 carb on it?

mtntopgeo

My Feedback: (12)

CP, Not too much available in wood, for the 7x4 size prop. NewZinger (lite-weight maple), New Top Flite (beechwood), & a fair amt of old Top Flite on the 'Bay. Any suggestions as to the best to start with.??? ......... RE your compression leak-down test; The engine will hold pressure in the comb. chamber for several seconds. Still has some pressure after 12 sec, or more. The original owner said that he only had a couple of tankfulls through it, & that appears to be true. .... A lot of "snap" when flipping over the prop.

YUU, Yes, I'm thinking that this might have a .15 size carb. (.275" port in the plug), but appears that the engine came from the manufacturer so equiped. ......... George K.

skaliwag

My Feedback: (1)

I have 3 of these engines... One has the super large hole and looks like it has never been run. The other 2 not so big but still looking far too big for the need.
I have never run them BTW.

combatpigg

My Feedback: (3)

Mntpgeo, sounds like you have a very nice engine, then. The TF props in the pylon series are the best to start with, but you can whittle on any of wood prop. The blades need to be thin, high aspect ratio, razor sharp trailing edges, tips that are zero thick. Make a tracing of the smallest blade once you arrive at a shape that looks about right, then use the tracing as a guide for the other blade. Keep your carver handy as you do tach tests, better yet, keep your knife handy during flight tests. You're going to need a small, clean airframe to reap the rewards, otherwise you could just do what you've already done, cut the tips off a 7x3 or 7x4 and go have some fun with a little 200 sq inch Q-200 type plane. I'll bet this engine would match up to the little Lanier racer with a 6.2x4 prop if you can get the rpms in the 20's. Just throwing some numbers around.

Make sure you run several tanks through it with small props and do a typical iron engine type break in before flying it with the needle set to "kill". This combo could really unload and fry an engine that isn't ready yet.

Skaliwag, shame on you for not running those engines! Do you think they would kick you out of Santa Cruz if you fired one up?